The present invention relates in general to transmission shift delay strategies and automotive heating, ventilating, and air conditioning (HVAC) systems. Such systems developed from the passenger's need for thermal comfort which has played an important role in automobile development since the very earliest days of vehicles. Early automobiles were fitted with interior heaters which depended variously on manifold heaters utilizing heated exhaust gases, gasoline-fired heaters, and heated engine coolant circulated through the engine, radiator and passenger compartment heater core.
As consumers demanded more comfort throughout the driving year and in more extreme climates, air conditioning systems were also introduced. Additional optional devices such as heated seats, cooled seats, heated steering wheels, or partitioned climate zones have become available for increasing comfort.
However, all of the air conditioning systems utilize energy and reduce engine performance, particularly at vehicle start up and during low speed drive-away or at speeds of about 50 kph or 30 mph. During vehicle start up and at such low speed drive-away passenger air-conditioned comfort is sometimes compromised while engine power is directed to the vehicle powertrain.
In response to this situation a transmission shift delay has been employed by some vehicle designers. The transmission shift delay is needed to keep engine RPMs high enough and, as a consequence, to maintain adequate revolutions of the clutched compressor to provide suitable air conditioning performance at high ambient temperatures.
The shift delay is usually time-based, timing out after perhaps 15 minutes at 50 kph/30 mph, for example. In some cases, the timed shift delay is not optimized and can be inappropriate in different temperature and road load scenarios, resulting in excessive fuel consumption on the one hand or poor air conditioning performance on the other hand. A more appropriate criterion for delaying transmission upshift is needed for optimizing powertrain performance while meeting customer comfort expectations through the achievement of optimum interior climate conditions.
As in so many areas of vehicle technology there is always room for improvement related to vehicle passenger comfort and fuel economy.